1. Technical Field of the Invention
The present invention relates to a suspension system suitable for a relatively small vehicle such as, for example, a saddle-riding type vehicle.
2. Background Art
An arrangement of a suspension system is known for a saddle-type vehicle, including a linkage mechanism disposed between a vertically reciprocally movable suspension arm and a vehicle body, and a shock absorber having one end connected to the linkage mechanism (see, for example, Japanese Laid-Open Patent Document No. Sho 62-61889.
In the known arrangement mentioned above, suspension performance can be improved by varying a stroke ratio (a ratio of an extension/contraction amount of the shock absorber relative to a vertical movement of a wheel) of the suspension system according to the vertical movement of the wheel. On the other hand, having the linkage mechanism separately from the suspension arm tends increase both the number of component parts used and the weight, and to impose restrictions on a degree of freedom in layout. In addition, the suspension arm is formed from a single member, which makes it difficult to tune the stroke ratio.
It is therefore an object of the present invention to enhance, in a vehicle suspension system having a vertically reciprocally movable suspension arm, the degree of freedom in layout and in setting the stroke ratio by minimizing the increase in the number of parts used and weight.
In order to solve the abovementioned problems, according to a first aspect of the present invention, there is provided a vehicle suspension system (for example, a front suspension 57 according to an embodiment of the present invention) includes a vehicle body frame (for example, a vehicle body frame 4 according to the embodiment of the present invention) that constitutes a vehicle body; a suspension arm (for example, a lower A-arm 62 according to the embodiment of the present invention) that has a first end pivotally attached to the vehicle body frame and a second end supporting a wheel (for example, a front wheel 2 according to the embodiment of the present invention).
The vehicle suspension system according to the first aspect also includes a shock absorber (for example, a shock absorber 58 according to the embodiment of the present invention) that has a first end connected to a side of the vehicle body frame and a second end connected to a side of the suspension arm. In this vehicle suspension system, the suspension arm includes: a first arm member (for example, a first arm member 65 according to the embodiment of the present invention) that has a first end pivotally attached to the vehicle body frame; a second arm member (for example, a second arm member 66 according to the embodiment of the present invention) that has a first end pivotally connected to a second end of the first arm member and a second end supporting a wheel; and a third arm member (for example, a third arm member 67 according to the embodiment of the present invention) that has a first end pivotally attached to the vehicle body frame and a second end disposed on the second arm member. Each of the first, second, and third arm members is pivotally connected to each other via a joint (for example, each of joints 68, 70 according to the embodiment of the present invention) and operatively associated with each other according to a vertical movement of the wheel to thereby cause the shock absorber to make a stroke motion.
According to another aspect of the present invention, the first arm member and the second arm member are disposed so as to form substantially a V-shape as viewed along a pivot shaft thereof.
According to still another aspect of the present invention, the second arm member is connected to both the second end of the shock absorber and the second end of the third arm member.
According to a further aspect of the present invention, the suspension arm is, in an independent suspension type suspension (for example, the front suspension 57 according to the embodiment of the present invention) having a knuckle (for example, a knuckle 63 according to the embodiment of the present invention) supported on distal ends of an upper arm (for example, an upper A-arm 61 according to the embodiment of the present invention) and a lower arm(for example, a lower A-arm 62 according to the embodiment of the present invention), the lower arm.
According to still another aspect of the present invention, the suspension system is a double wishbone type suspension for a front wheel in a rear-wheel-drive all-terrain vehicle (ATV).
According to the first aspect of the present invention, a linkage mechanism can be formed from the suspension arm that includes a plurality of arm members without having a linkage mechanism separately, so that the number of parts used and weight of the suspension system can be minimized to thereby enhance a degree of freedom in layout and a degree of freedom in setting the stroke ratio of the suspension system.
According to the second aspect of the present invention, the distal portion of the shock absorber can be connected near a bottom portion of the suspension arm that is substantially formed into a V-shape in a view as viewed in the direction of the pivot shaft. The shock absorber can be disposed at a lower level for a lower center of gravity and a stroke amount of the shock absorber can be increased.
Further, according to the third aspect of the present invention, the shock absorber can be disposed at an even lower level for an even lower center of gravity and a stroke amount of the shock absorber can be further increased. This is particularly effective in applying the present invention to a suspension system for a all-terrain vehicle.
For a more complete understanding of the present invention, the reader is referred to the following detailed description section, which should be read in conjunction with the accompanying drawings. Throughout the following detailed description and in the drawings, like numbers refer to like parts.